feat: wip ISSUE-32936 adding support for AdditionalMappingContributions

Author: NickBeginner

extensions/hibernate-orm/runtime/src/main/java/io/quarkus/hibernate/orm/runtime/boot/FastBootMetadataBuilder.java

@@ -165,19 +165,23 @@ public FastBootMetadataBuilder(final QuarkusPersistenceUnitDefinition puDefiniti
          * of the destroyed service registry in PreconfiguredServiceRegistryBuilder.
          *
          */
-        for (Class<? extends Service> postBuildProvidedService : ssrBuilder.getPostBuildProvidedServices()) {
-            providedServices.add(new ProvidedService(postBuildProvidedService,
-                    standardServiceRegistry.getService(postBuildProvidedService)));
-        }
+        ssrBuilder.getPostBuildProvidedServices()
+                .forEach(serviceClass -> providedServices.add(
+                        new ProvidedService(
+                                serviceClass,
+                            standardServiceRegistry.getService(serviceClass)
+                        )));
 
         final MetadataSources metadataSources = new MetadataSources(ssrBuilder.getBootstrapServiceRegistry());
+
+        applyMappingContributors(metadataSources);
+
         // No need to populate annotatedClassNames/annotatedPackages: they are populated through scanning
         // XML mappings, however, cannot be contributed through the scanner,
         // which only allows specifying mappings as files/resources,
         // and we really don't want any XML parsing here...
-        for (RecordableXmlMapping mapping : puDefinition.getXmlMappings()) {
-            metadataSources.addXmlBinding(mapping.toHibernateOrmBinding());
-        }
+        puDefinition.getXmlMappings()
+                .forEach(mapping -> metadataSources.addXmlBinding(mapping.toHibernateOrmBinding()));
 
         this.metamodelBuilder = (MetadataBuilderImplementor) metadataSources
                 .getMetadataBuilder(standardServiceRegistry);
@@ -651,6 +655,10 @@ protected void populate(MetadataBuilder metamodelBuilder, List<CacheRegionDefini
         }
     }
 
+    private void applyMappingContributors(MetadataSources metadataSources) {
+
+    }
+
     private void applyMetadataBuilderContributor() {
         Object metadataBuilderContributorSetting = buildTimeSettings
                 .get(JpaSettings.METADATA_BUILDER_CONTRIBUTOR);